The button is shown only when all of these are true: your account has the Retail module, the Retail setting Retail Menu AI Upload (show the "Update Stock with AI" button) is set to Yes (it is on by default), and you are on the Retail Menus list or a retail location's menu page. Using it also requires the Edit Retail Menus permission – otherwise the upload is refused with You do not have permission to update retail stock. If the setting is off you get The AI stock upload is not enabled for this account.